Screw and nut mechanism



Dec. 11, 1951 c. L, SHULL SCREW AND NUT MECHANISM Filed Feb; 19, 1949 INVENTOR. fiw/eauCSfiull BY A TORNEY WI TNESS. im. 66/7 Patented Dec. 11, 1%1

UNITED STATES .PATENT OFFICE SCREW AND NUT MECHANISM Charles L. Shull, Horseheads, N. Y.

Application February 19, 1949, Serial No. 77,380

3 Claims. (01. 74-4243) The present invention relates to a variable electrical capacitance, and more particularly to a trimmer condenser for use in connection with tuned radio-frequency electrical circuits.

Variable condensers of this general type are commonly formed of telescoping cylindrical members separated by an air space or by other suitable dielectric material such as a vitreous, ceramic or plastic tube. In order to vary the capacity of the condenser, the inner electrode is adjusted longitudinally with respect to the outer electrode so as to increase or decrease the amount of overlap between them, this being usually accomplished by some form of threaded connection to facilitate fine adjustment.

In devices of this type as heretofore constructed however, it has been difiicult to secure smooth adjustment, free from fluctuation and/or microphonic noises due to wobbling or irregular movements of the movable electrode, particularly when the threaded adjusting means therefor requires that the electrode be rotated in order to vary the capacity of the condenser.

It is an object of the present invention to provide a novel variable condenser of the tubular type which is simple in construction, efiicient in operation and economical to manufacture.

It is another object to provide a device in which the variations of capacity take place smoothly and without fluctuations or microphonic disturbances.

It is another object to provide such a device in which the movable electrode is arranged to slide into and out of the outer electrode without relative rotation or wobbling.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation, partly broken away and in section, of a preferred embodiment of the invention;

Fig. 2 is an end view thereof;

Fig. 3 is a section taken substantially on the line 33 of Fig. 1;

Fig. 4 is a detail in perspective of the mounting bushing for the condenser prior to the insertion of the control nut therein, together with the anchorage means for the bushing shown separate therefrom; and

Fig. 5 is a detail in perspective of the square threaded adjusting bar.

In Fig. 1 of the drawing there is illustrated a tube i of suitable dielectric material such as glass, having an outer electrode 2 mounted there- .on and extending from one end thereof substantially to the middle of the tube. The electrode 2 may be a metallic cylinder, or a metallized coating of the glass, and is preferably provided with a connector 3 which may be soldered or otherwise suitably anchored and fixed to the end of the tube and the electrode.

An inner electrode 4 of suitable material such as Invar is slidably mounted within the tube 1, and means are provided for moving this inner electrode longitudinally to adjust its telescopic relation with the outer electrode 2 in order to vary the capacity of the condenser. As here shown, this means comprises a shaft or bar 5 of uniform non-circular cross section, a square cross section as illustrated being preferred. Electrode 4 is rigidly mounted on one end of the bar 5 in any suitable manner as by crimping the bar in a counter-bore thereof as indicated at 6.

The bar 5 extends outside of the tube l, and a bearing bushing l therefor is suitably fixed to the end of said tube as by soldering to a metallized coating thereon as shown at 8. The bushing 7 has a non-circular central bore 9 conforming closely to the bar 5 and slidably receiving said bar while preventing relative rotation. The angular edges of the bar 5 are threaded as shown at H, and a nut I2 is threaded on said bar and has an enlarged portion l3 seated in a counterbore it in the outer end of the bushing i and retained therein by lips or flange members l5 (Fig. 4) which are bent down over the end of the enlarged section 83 after the same has been inserted in the counter-bore of the bushing. A flexible washer I6 is preferably interposed between the inner end of the nut I2 and the bottom of the counter-bore I4 in order to prevent lost motion of the nut with respect to the bushing l and also to frictionally resist rotation of the nut so as to maintain the adjustment of the condenser. The portion of the nut which extends outside the bushing is preferably formed with flats or slots 2!! to receive a spanner or wrench to facilitate adjustment. I

The bushing l is arranged to be rigidly mounted in a panel or chassis member such as indicated at ll. For this purpose, the bushing is provided with a portion 98 having a non-circular external conformation which may comprise one or more flats l9, adapted to be received in an opening 2| in the panel. 11 I having a similar conformation. A shoulder 22 is arranged to engage one side of the panel ii, and an elastic U-shaped retaining member 23 is adapted to be slidably received in a groove 24 in the bushing and bear against the opposite side of the panel to thereby hold the bushing rigidly assembled in the panel.

It will be readily appreciated that the smooth fiat surfaces of the square bar 5form an excellent bearing in the square bore of the bushing I, while the spring-loaded nut l2 assists in maintaining the alignment of the bar in the bushing while cooperating with the threaded corners of the bar to provide a-convenient and accurate means for adjusting the bar 5 and electrode 4 longitudinally.

Although but one form of the invention has been shown and described in detail, it will be understood that other embodiments are possible, and

bar having an'enlarged portion seatedin the counterbore of the bushing, said bushing having a terminal flange embracing the end of the enlarged portion of thenut to retain it in the counterbore while permitting rotation thereof to traverse the threaded bar, theexterior of the bushing having a cylindrical surface provided with a flattened portion'and a radial flange adjacent thereto, a fixed panel having "an opening conforming to the flattened cylindrical surface, and. detachable elastic means for clamping the bushing in said opening with the flange bearing on the panel.

2. Mounting and adjusting means as set forth in claim 1 including further an elastic compression member seated in the bottom of the counterbore in the bushing and bearing against the end of the nut to remove backlash between the nut and. bushing, and to frictionally maintain the adjustment of the nut and bar.

3. Mounting and adjusting means as set forth in claim 2 in which the projecting portion of the nut is formed to receive a rotary adjusting tool, and including further means for non-rotatably mounting the bushing in a fixed support.

CHARLES L. SHULL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,067,104 Fitzpatrick -Ju1 *e,19 13' 1,200,689 Anderson i Oct; 19,1916 1,261,531 Hindman et al. Apr; 2,1918 1327,93 1 Alcock a Jan.- 13, 1S20 1333,70? Dies Mar. 16, 1928' 1,641,438 Jones Sept. 6, 1927 2,185,056-1 Ehrlich Dec. 26,1939- FOREIGN PATENTS.

Number" Country: Date 263,948 Great Britain; M Jan. 10, 1927 

